Lice infestation on the human body (also known as pediculosis) is very common. Cases number in the hundreds of millions worldwide. Certain lice, such as body lice, can transmit diseases, such as typhus, relapsing fever, and trench fever, but most of the time having lice is more embarrassing and itchy than it is concerning as a disease.

Lice are tiny, wingless, parasitic insects that feed on your blood. This itchy infestation is easily spread -- especially by school children -- through close personal contact and by sharing personal belongings.

Several types of lice exist:

Head lice. These lice develop on your scalp. They're easiest to see at the nape of your neck and over your ears. Small eggs (nits) produced by lice attach to your hair shafts. The eggs hatch in about one week, resulting in more lice.

Body lice. These lice spend most of their time in the seams and folds of your clothing. Body lice are often spread by direct contact with infected clothing or bedding or with an infected person. In rare cases, body lice may carry diseases.

Pubic lice. Commonly called crabs, these lice occur on the skin and hair of your pubic area and on eyelashes. Sexual contact or contact with infected clothing, bedding or even toilet seats can spread pubic lice.

If you have lice, this is a medical condition! You should consult a physician or use nonprescription anti-lice agents containing permethrin and/or pyrethrin. DO NOT USE ANY HOUSEHOLD INSECTICIDE OR PEST CONTROL PRODUCT ON YOUR BODY - THIS CAN RESULT IN SEVERE REACTIONS AND EVEN DEATH!

Facts About Lice

Three different types of lice infest people:

Head lice (Pediculus humanus capitis): Head lice are the most common. The Centers for Disease Control and Prevention (CDC) reports that 6-12 million people in the United States are infested each year with head lice.

Children aged 3-10 years in preschool, elementary school, or daycare centers are most likely to have lice. All socioeconomic classes are affected.

Lice can appear in anyone's hair (more common in girls than boys), no matter what hair length or the person's degree of cleanliness. Lice are seen less often, however, in African Americans due to hair type.

Head lice will not infect dogs, cats, or other pets.

Head lice are transmitted mainly through head-to-head contact (sharing pillows, lying on carpet, wearing someone's hat). Head lice cannot jump or fly, so sitting near someone will not transmit lice. Indirect contact, such as with brushes and bed linens, is less likely to lead to transmission because the louse dies if away from the scalp for more than 2 days.

Head lice can be found behind the ears and near the hairline at the neck -- but can be difficult to see (They can change color to match the hair.) Nits look like whitish shells found on the hair strand near the scalp. They are firmly attached to the hair shaft and cannot be flicked off easily. You may have scalp itching, redness, and crusting or no symptoms at all. However, it can result in skin infections, especially if the bites are repeatedly scratched. Infection can lead to swollen nodes that form lumps behind the ears and on the neck.

Body lice (Pediculus humanus corporis): Body lice are seen more often in underdeveloped countries but also among the homeless population in the United States. Body lice are associated with poverty, overcrowding, and poor hygiene.

Body lice infestations occur more often when clothes are not changed or washed frequently.

Body lice live in the seams of clothing (not in the hair) where they lay their eggs but go to the body to feed�most often to the back, shoulder, and waist.

Bed bugs are related to lice. They hide among sheets and blankets and really do bite during the night when they seek a warm body for a meal. They usually leave brown or black markings on the bed linen and bite in rows, often leaving 3 or more linear bite marks.

Body lice are transmitted by direct contact with an infected person. Body lice are frequently seen among the homeless and others living in overcrowded conditions, where clothes are not washed often and where overall cleanliness is lacking.

Lice and nits are found in seams of clothing. Red, itchy bite marks may be seen on the body. With infected scratch marks, there is increased pain, redness, swelling, or drainage. Itching is often worse at night and in the elderly can cause insomnia.

Pubic lice (Pthirus pubis): In general, pubic lice are transmitted by intimate or sexual contact. The lice look like tiny crabs, which is why someone may say they have a "case of crabs." Affected people should be checked for other sexually transmitted diseases. Pubic lice or crabs are often found in the genital area but can spread to the lower abdomen, armpits, eyelashes, and even scalp.

Contrary to popular thinking, pubic lice are not spread by toilet seats.

Condoms do not protect you from getting pubic lice.

Pubic lice are transmitted by direct sexual contact. In children, pubic lice are generally contracted from an infected parent. In children, they are rarely sexually transmitted. But sexual transmission is possible in situations of sexual abuse. Transmission via bed linens and infested clothing is less likely and doubted by some.

With close inspection, lice and nits can be seen on pubic hair. They cause intense itching, particularly at night. After being bitten, a bluish-colored sore may develop on the thighs and trunk.

Tips for controlling Lice

Lice can effectively be treated with home care methods. But call the doctor if these conditions develop:

If skin or scalp infections develop from scratching, with symptoms such as redness, swelling, pain, or tenderness to the area.

If home treatment doesn't work after using over-the-counter medications as directed.

For further testing for sexually transmitted diseases (if pubic lice are discovered).

If itching continues even after treatment with over-the-counter antihistamines.

If lice persist and treatment has failed, recheck for a change in anti-lice treatment.

If you develop an allergic reaction to medications (indicated by a rash, swelling to the lips or tongue or if you have any trouble breathing) OR if infections from scratching are not improving, are worsening while you are on medications, or if other symptoms develop such as fever, chills, nausea, and vomiting - GO TO THE HOSPITAL IMMEDIATELY

Head lice Search for head lice when hair is wet. Use a fine-toothed comb (or a louse comb), clear tape (to stick on hair to pick up nits), a magnifying glass, and a strong light. Wet combing should be done every 2-3 days over a 2-week period, with small sections of hair, working out from the scalp. Some call this "bug busting," and it can be very effective. If lice are found, treat with an anti-lice agent and repeat in 7-10 days to kill newly hatched nits. Over-the-counter treatment is available and should be used first. If after 2 applications, lice are still present, then prescription anti-lice agents may be needed from your doctor. Apply the anti-lice agent to dry hair for the time listed on the product (usually 10 minutes). Shampoo and rinse hair and comb as directed with a fine-toothed comb. Repeat anti-lice treatment in 7-10 days to kill nits that may have hatched. Nonprescription anti-lice agents include Nix Lotion (permethrin 1%) and Rid, A200, and Pronto shampoos (pyrethrin products).

Check all household members and treat only if lice or nits are seen. If a child is younger than 2 years, comb to remove lice and nits but do not use anti-lice agents. Hair conditioners may coat or cover the lice, so they should not be used before applying anti-lice agents. Wash all bed linens and clothing that have been in contact with the infested person in the past 2 days. Use hot water and the hot cycle in the dryer. Some recommend that water be at least 140�F to effectively kill the lice and nits. Most hot-water heaters are set at 120°F for child safety. This lower temperature may be effective. All nonwashable items such as stuffed animals should be placed in plastic bags for 2 weeks then opened outdoors. Dry cleaning may be an alternative. Disinfect combs and brushes in hot water or alcohol. Soak for more than 5 minutes in very hot water (greater than 131°F or 55°C). Vacuum floors and furniture, especially couches and areas used by children. Throw away the vacuum bag immediately. Herbal therapy and oil treatments have not been proven to work.

Do not use gasoline, kerosene, or oils. Burns have occurred. Do not shave the person's head. This drastic measure is not necessary. If lice are seen in a school-aged child, notify the school nurse or teacher in order to limit the spread.

Body lice ash the body thoroughly. Wash and dry all bed linens and clothes in hot cycles. Destroy what you can because these nits can survive longer without human contact. Anti-lice agents are usually not needed if clothing is thrown away and bed linens are thoroughly washed. Check all household members or close contacts. Treat them only if lice or nits are seen. Vacuum floors and furniture. Throw the vacuum bag away immediately. Chemical insecticide sprays in the home are not effective and not recommended. Use over-the-counter antihistamines (such as diphenhydramine, Benadryl) for itching.

Pubic lice Treat with anti-lice agents and repeat in 7-10 days. Remove nits with a fine-toothed comb. Check all close contacts. Treat them only if lice or nits are found. Wash and dry all clothes and bed linens in hot cycles. Check eyelashes and eyebrows. If lice or nits are seen, apply petroleum jelly (Vaseline) twice daily for 8 days. Use over-the-counter antihistamines (such as diphenhydramine, Benadryl) for itching.

Families are encouraged to look for lice routinely because it can recur.

Safe sexual practices may lower the risk of transmitting pubic lice and other diseases.

Wash clothes, bed linens, combs, and brushes to prevent recurrence.

Preventive treatments with anti-lice agents are NOT recommended and can lead to illness and persistent itching.

With appropriate home care or prescription medication, more than 90% of lice infestations can be cured. Treatments are more effective in killing lice than nits. This is why combing is so important to remove nits�as is repeating the anti-lice treatment in 7-10 days. Children can return to their usual activities and school or daycare after the first treatment, even if nits are still in the hair. Re-treat in 7-10 days as discussed above.